This invention relates to a gas flow controlling device and to a soldering apparatus using same.
A molten metal such as molten solder is apt to be oxidized when contacted with air. To cope with this problem, an inert gas such as nitrogen is continuously streamed to a mass of the molten metal to form an oxygen-free atmosphere therearound.
JP-A-7-185790 discloses a device for soldering printed wiring boards as shown in FIGS. 12 and 13. Designated as 1 is a solder vessel for containing a molten solder 2. The molten solder 2 is upwardly ejected by a pump 3 to form a solder wave 4. An inert gas feeder having a square ring 5 is supported by bars 6 on the vessel 1 to surround the surface 4a of the solder wave. The ring 5 is provided with a multiplicity of injection holes 7 from which an inert gas supplied from a gas feed pipe 9 is injected toward the solder wave surface 4a to form an inert gas atmosphere 8 over the solder wave surface 4a. The known soldering device has a problem because air surrounding the jetted inert gas atmosphere 8 is sucked thereinto so that the oxygen concentration of the inert gas atmosphere is not sufficiently low, whilst a relatively large amount of the inert gas is consumed.
JP-A-8-39829 discloses a device for wave soldering printed wiring boards. The solder wave is covered with a casing in which an injection nozzle is disposed. An inert gas is injected from the nozzle toward the solder wave to maintain the space within the casing in the inert gas atmosphere. This soldering device, too, has a problem that air is sucked in the casing by the jet flow of the inert gas. Additionally, air enters the casing through inlet and outlet openings thereof for the printed circuit board to be soldered.